Mobile communication systems developed to provide the subscribers with voice communication services on the move. With the rapid advance of technologies, the mobile communication systems have evolved to support high speed data communication services as well as the standard voice communication services. However, the limited resource and user requirements for higher speed services in the current mobile communication system spur the evolution to more advanced mobile communication systems.
Meanwhile, Internet Protocol Multimedia Subsystem (IMS) is an architectural framework for delivering multimedia services on the IP-based network unlike the circuit-switched centric network system dedicated to the basic voice telephony service. Recently, IMS is becoming the key technology in the next generation communication systems because it improves the wired and wireless network services flexibility and thus contributes to the network convergence, resulting in reduction of application development and management costs and increase of service diversity with novel applications such as VoIP, Instant messenger, and Push To Talk (PTT).
In the IMS-based mobile multimedia communication system, the terminals negotiate communication conditions and reserve radio resource of the network based on the negotiated conditions.
In the conventional system, however, if it is difficult to allocate the resource to the terminal as much as fulfilling the negotiated conditions, the network rejects the resource reservation request of the terminal without notification of the reason for the reject.
Accordingly, when rejecting the radio resource request, there is a need of providing the terminal with any information to help the terminal take any subsequent action.